I think you missed my point. One of the 10 Kings, the 5th one, is a Jizou statue. Yes, employment of Jizou statues happens after the 10 Kings, but that is something else.
Jizou statues are modeled after
the Jizou. They are representations of the deity Jizou Bosatsu. The fifth King was not a Jizou statue. The lines in the religion get really wonky here, because Jizou Bosatsu itself is not actually Enmaou either; despite being the "same", the 10 Kings of Hell are slightly separate notions from the 13 buddhist deities.
The Jizou statues themselves have also essentially split apart from their original purpose, since originally they're put up to be signs of Jizou Bosatsu helping the living and dead in some manner. However, they sort of evolved into their own thing on their own, and are much more well-known than the 10 Kings, and even the buddhist deities themselves.
Anyways, I think it's apparent by now that there's an iffy wording in the text that misled the translation.
First, there were the Ten Kings; the fifth of which was 閻魔王 Enmaou. The others were not Enma/Yama, but they were all 裁判官 judges. When the number of humans to judge became too much to handle in so many steps of judgement, 十王全てが all of the Ten Kings [subject] looked to 当時最も力のあった the most powerful (i.e. in judgement) at the time [qualifier] 閻魔王 Enmaou [object], and を名乗る impersonated them, 審判を一回だけに減らす事で to reduce the judgements to only one.
This is why they all now have the name of 閻魔 Enma/Yama.
Then the Jizou statues were appointed as new 閻魔 Yama, which are now established to be the 裁判官 judges. Now, 殆どの閻魔様は、古いお地蔵さんである nearly all Yama are old Jizou statues.
The Ten Kings at the top of the Ministry are 十人の閻魔王 the ten "Enmaou", i.e. those who are now named Enmaou. Below them are other 裁判官 judges and the kishin chiefs.
Another mistranslation now caught: このうち、裁判官までが閻魔と呼ばれるのである Among these, all up to the judges can be referred to as Enma/Yama.
裁判官 also does not refer to "lesser" judges either, just the judges. All of which are called Yama. This clears up the fact that
all judges are given a region to be in charge of.
意見 also does not mean testimony, it simply means their opinion. This alleviates the problem mentioned before, since it isn't their testimony that's unheard; simply their opinion on where they should go or what deed is considered righteous or a sin, which is obvious.
The mixing of all these religious premises is all acknowledged and is why the Jizou statues are the ones being upgraded into Yama; the Jizou statues are representations of the deity whose counterpart is the King whose name the rest took on. Therefore, they all are actually called Yama. Ha.